1. Field of the Invention
The present invention relates to a method of manufacturing amorphous metal oxide films and methods of manufacturing a capacitance element having an amorphous metal oxide film and a semiconductor device having an amorphous metal oxide film, e.g., methods of manufacturing an electrostatic capacitance element using an amorphous metal oxide film formed of an amorphous tantalum oxide thin film as a dielectric insulation film, e.g., a semiconductor device including an amorphous tantalum oxide thin film.
2. Description of the Related Art
Semiconductor devices, e.g., semiconductor integrated circuit devices, generally use a nitride silicon film (Si3N4 film) as a capacitive insulation film of an electrostatic capacitance element. As demand for the microminiaturization of semiconductor devices and the demands for increased degrees of integration and increased operation speeds for semiconductor devices progressively increase, various studies and developments for depositing Al2O3 films, oxide tantalum films, BaSrTiO films, SrTao films and PbTiO3—PbZrO3 films have been made so far. Of these metal films, tantalum oxide films have received remarkable attention. When a capacitance element having an MIS (metal-insulator-semiconductor) structure is formed, the following method is now frequently used to deposit a tantalum oxide film of its capacitive insulation layer, for example. FIG. 1 is a schematic flowchart to which reference will be made in explaining a method of depositing a tantalum oxide film. As shown in FIG. 1, a substrate, e.g., a semiconductor wafer, is introduced into a low-pressure CVD (chemical vapor deposition) method system at a step S1, whereafter a tantalum oxide film is deposited at a step S2. In general, when most of the tantalum oxide film is deposited, pentaethoxytantalum (Ta(OC2H5)5) is used as a raw material, vaporized and then reacted with oxygen at a heat energy of about 450° C. under reduced pressure.
However, according to this film deposition method, a large amount of carbon (C) and hydroxyl group remains in the deposited film. Moreover, there is deposited a film which is in short of oxygen so that Ta and O cannot be coupled sufficiently.
As a result, only by this deposited film, there cannot be obtained sufficient electric characteristics, in particular, a leakage current characteristic, a withstand voltage characteristics, a dielectric constant and so forth.
To solve these problems, it is necessary to carry out a film quality improvement treatment. In this film quality improvement treatment, the deposited film is conveyed from the above-mentioned low-pressure CVD system into a film quality improvement system, e.g., an ultraviolet-ray radiation anneal treatment (so-called UV—O3 treatment) system, at a temperature ranging from 400° C. to 500° C. in the atmosphere of ozone at a step S3, wherein the deposited film is annealed at a step S4. Then, the wafer thus annealed is taken out from this treatment system at a step S5 and is then further annealed at a temperature in excess of 600° C. in an atmosphere of oxygen at a step S6.
The above-mentioned film is deposited by a general multi-chamber CVD system. FIG. 2 is a diagram showing a schematic arrangement of such a multi-chamber CVD system. As shown in FIG. 2, this multi-chamber CVD system includes four chambers 101a to 101d at maximum prepared for a substrate, for example, a wafer conveying chamber in which a substrate or wafer is deposited. The substrate is transported from substrate cassette load-lock chambers 102 by a transportation robot 103 into the respective chambers 101a to 101d and vice versa.
Then, in this system, the two chambers are configured as film-deposition chambers and the remaining two chambers are configured as UV—O3 chambers serving as chambers in which wafers are treated after oxidation. A tantalum oxide film is deposited by any one of the film-deposition chambers and is treated by a post-treatment process in any one of the UV—O3 chambers.
The tantalum oxide film thus treated by the post-treatment process is then annealed at a temperature higher than 600° C. in the oxygen atmosphere containing at least oxygen and thereby can be improved in quality.
However, in recent years, semiconductor devices have been required to operate at higher speeds. Hence, there is a trend that necessary layers such as electrode layers and interconnection layers should be formed of metal layers progressively. In accordance with the above-mentioned increasing demands and trends, in the semiconductor device manufacturing process, it is requested that a heat-treatment process be made at lower temperatures. For example, there is an increasing demand that a capacitance element serving as a circuit element in a semiconductor integrated circuit introduce a so-called MIM (metal-insulator-metal) structure obtained when an electrode layer or an interconnection layer is formed of a metal layer.
When the capacitance element having the MIM structure or the like is formed under the above-mentioned circumstances, if a metal oxide film such as a tantalum oxide film is formed as a dielectric insulation layer by the above-mentioned film-deposition method which requires the above-mentioned high-temperature treatment, then problems will arise in the characteristics and reliability of the capacitance element, i.e., the semiconductor device.
Specifically, in the stage in which the metal film that requires the above-mentioned high-temperature treatment is formed, when the metal layer has already been existing, i.e., a metal layer has a structure in which an electrode metal layer of a lower layer has already been existing in the MIM structure, this metal layer has to be formed of high-melting point metals which are rich in heat-resisting properties and which are low in resistivity, e.g., expensive metals such as Pt (platinum) and Ru (ruthenium). However, these metals inevitably encounter poor workability obtained when these metals are formed as microminiaturized patterns. Moreover, it is unavoidable that these metals require complex manufacturing processes and complex manufacturing facilities, such that the metal layers become expensive.
On the other hand, as a substitute technology for the above-mentioned post-treatment with high temperature, there has been examined so far a method in which a metal layer is processed by an O2 plasma oxidation treatment after the metal layer had been deposited. FIG. 3 is a flowchart to which reference will be made in explaining the above-mentioned substitute technology. As shown in FIG. 3, a substrate, e.g., a semiconductor wafer, is introduced into a low-pressure CVD method system at a step S10, whereafter a tantalum oxide film is deposited on the semiconductor wafer at a step S11. Then, the deposited film is transported from the above-mentioned low-pressure CVD system into the film quality improvement system, e.g., ultraviolet-ray radiation anneal treatment system, at a temperature ranging from 400° C. to 500° C. in the atmosphere of ozone at a step S12, wherein the deposited film is processed by an O2 plasma treatment at a step S13. Then, the semiconductor wafer thus processed by the O2 plasma treatment is taken out from this treatment system at a step S14. However, a plasma oxidation treatment executed by a general diode parallel plate plasma treatment system fails to provide sufficiently high film characteristics.
Furthermore, in this case, it is necessary to prepare both a CVD system for depositing films and a high-density plasma system. Even when these systems are formed as a single system, it is unavoidable that metal layers should be produced expensively.